DC-DC Power systems have been using a plurality of converters connected in series-input and parallel-output configurations. Uniform output current-sharing and nonuniformly input voltage distribution exists as a result of mismatches in component values employed among nearly-identical series-input converters having outputs connected in parallel. With such mismatches, output voltage regulation performance becomes unreliable in both the steady state and the transient state because the input voltages across individual converters drift too far from a uniformly distributed voltage. Undesirable interactions among interconnected converters arise because of drifted nonuniform input voltage distribution that leads to instability due to different modes of operation among series-input converters, each of which is controlled differently under respective dedicated voltage regulation control.
DC-DC Power systems employing converters connected in parallel-input and parallel-output configurations are well known. The problem of uniform current distribution control is solved by using the manufacturer-provided parallel control port that serves as a common shared-bus, at which a single input voltage commands the parallel-connected converters to operate as voltage-controlled current-sources. This current-mode shared-bus approach to uniform current distribution is well established, particularly for parallel-connected conventional converters.
DC-DC converters can be connected in a distributed-input parallel-output configuration where the converter outputs are parallel connected to a common load and the inputs are individually connected to the distributed input power sources. The distributed sources may have non-identical characteristics that result in non-uniform distribution of the converter input voltages in addition to minor internal component mismatches among these converters. When each of the distributed input power sources is independent and not coupled to the other input power sources, the nonuniform input voltages may not become an issue because the system can achieve robust stability without dedicated uniform input voltage distribution control. However, when converters are connected in a series-input parallel-output topology that shares a common input power source across the series-connected converter inputs, the non-uniformly distributed input voltages can also lose stability and cause one or more of the converters to absorb an excessive portion of the common system input voltage. System reliability suffers because the converters that contribute a greater portion of the output power are thermally overstressed. These and other disadvantages are solved or reduced using the invention.